1. Field of the Invention
The present invention relates to a mobile communication method suitable for a purchased mobile unit system, and also relates to a mobile telephone switching station, a customer management system, and a mobile unit for implementing the same.
2. Description of the Related Art
For mobile units used as mobile telephones such as car telephones, portable telephones, etc., Japan currently adopts leasing systems under which subscribers lease mobile units from common carriers providing mobile telephone networks, but a purchased equipment system is expected to be introduced soon whereby the user can purchase a mobile unit. While it is hoped that the introduction of the purchase system will contribute to more widespread use of mobile telephones, it may give rise to problems such as illegal duplication of mobile units (clone mobile units). In fact, other countries where purchase systems are adopted are already facing such problems.
There are two types of information stored in the memory of a mobile unit: information such as built-in software, whose contents are identical with other mobile units of the same model, and information that is different for each individual mobile unit and is used to authenticate the mobile unit to the communication network for connection. The former type of information need not be read out or written in from the outside, and also, the amount of information is large; therefore, it is hard or impossible to read out or write in the information from the outside. On the other hand, the latter type of information includes information concerning the telephone number (Mobile Subscriber Number: MSN) assigned to each individual subscriber of the telephone network, the mobile unit number (Mobile Station Identity: MSI) for identifying each individual mobile unit, the authentication key (MSN-key) for the communication network to authenticate the subscriber, and the authentication key (MSI-key) for the communication network to authenticate the mobile unit. The amount of such personal information is relatively small. Once the mobile unit lump-sum purchase system is put into operation, it will become necessary that when a contract between the common carrier and the subscriber who purchased a mobile unit is made after the sale of the product, the personal information be written into the mobile unit for registration with the common carrier as soon as possible; to achieve this, provisions must be made so that such personal information can be readily written in and read out from the outside. Furthermore, the personal information must be alterable to allow for a possible future change in the contents of the contract.
In other countries where mobile unit purchase systems are already adopted, a stand-alone ROM writer is installed at a mobile unit shop, and each mobile unit, upon sale, is connected to the ROM writer to write the necessary personal information into an internal EEPROM of the mobile unit.
This method of writing personal information using a ROM writer, however, entails the problems described below.
(a) To make the mobile unit available to the subscriber for use when the contract is made, as many ROM writers as the number of mobile unit models carried or the number of common carriers contracted need to be installed at the mobile unit shop. This increases the sales cost.
(b) Because of human intervention when writing the personal information by using the ROM writer, there is a danger that the ID (identification information) may fall into the wrong hands.
(c) Since mobile units are shipped from factory with no personal information written therein, mobile units cannot be subjected to communication connection tests at the factory prior to shipment. (This means that there is a possibility that defective products may be delivered to users).